Slidable tray insert for a mailbox



FIG. 1 is a top, front and right side perspective view of a slidable tray insert for a mailbox showing our new design;

FIG. 2 is a front elevational view;

FIG. 3 is a rear elevational view;

FIG. 4 is a top plan view;

FIG. 5 is a right side elevational view;

FIG. 6 is a left side elevational view; and

FIG. 7 is a bottom plan view thereof. 

The ornamental design for a slidable tray insert for a mailbox, as shown. 